1. Field of the Invention
This invention relates in general to staircases, and in particular to a metal staircase for use in buildings with two or more floors.
2. Description of the Prior Art
Essentially all multiple floor buildings must have one or more staircases. In buildings with two or more floors, the staircases are primarily for emergency use, and are not often used by occupants of the building. Since they are normally not visible, the architects desire an inexpensive nonornamental staircase that meets building code requirements. The buildings will have reinforced concrete floors or structural steel frames with deck and concrete fill. The staircases will have a metal frame, usually with concrete poured in each step and at the landings after erection.
The most commonly used method in construction consists of constructing at a factory a lower flight assembly and an upper flight assembly for each section of the staircase between floors. If the staircase is a right hand staircase, with the wall on the right as the user ascends, then the lower flight assembly will consist of a pair of stringers with steps welded between. Just past the top step, the right hand stringer for the lower flight assembly will have a horizontal channel member extending forwardly to form one side of the landing. The upper flight assembly will have a horizontal channel member extending from the bottom of its right stringer to form the other side of the landing.
To erect a section between floors, both the upper and lower flights must be suspended in place. A back channel member is then attached to the horizontal members to form the landing. Then a header member is installed to support the center part of the stair flight. The flight assemblies are secured together and a plate is placed over the landing members to define a landing. This is a cumbersome and time consuming operation since two flight assemblies have to be suspended at the same time.
Because of the horizontal channel members being secured to the flight assemblies at the factory, the upper and lower flight assemblies cannot be interchanged. If the building requires two staircases, one right hand and the other left hand, the flight assemblies for the right hand staircase cannot be interchanged with the flight assemblies for the left hand staircase. This requires an additional number of noninterchangeable parts, thus adding to the cost of the staircases.
Recently, staircases have been made by first constructing the landing, then securing the upper and lower flight assemblies to it. However, the connection means are complex and the flight assemblies are not interchangeable.